DBus listen(number<s>) and daemon \-\-number

implement listen method for DBus
listen(number<s>) -> <>::

add \-\-number option to daemon subcommand
- permits starting daemon in anonymous mode with zero or more numbers
- numbers may be added to daemon with listen() and removed with unlisten()

change misleading "dataPath" to `settingsPath` in App.java
- settingsPath=~/.local/share/signal-cli, while dataPath=~/.local/share/signal-cli/data

only use FileLock when necessary in App.java, and unlock when appropriate

update documentation

man/signal-cli-dbus.5.adoc

@@ -67,6 +67,14 @@ listAccounts() -> accountList<as>::
 
 Exceptions: None
 
+listen(number<s>) -> <>::
+* number            : Phone number
+
+Starting checking the Signal servers on behalf of this number, and export a DBus object path for it. 
+Fails if user is not already registered.
+
+Exceptions: Failure
+
 register(number<s>, voiceVerification<b>) -> <>::
 * number            : Phone number
 * voiceVerification : true = use voice verification; false = use SMS verification
@@ -78,6 +86,8 @@ registerWithCaptcha(number<s>, voiceVerification<b>, captcha<s>) -> <>::
 * voiceVerification : true = use voice verification; false = use SMS verification
 * captcha           : Captcha string
 
+Captcha strings may be obtained from `https://signalcaptchas.org/registration/generate.html`
+
 Exceptions: Failure, InvalidNumber, RequiresCaptcha
 
 verify(number<s>, verificationCode<s>) -> <>::